The SPE Library contains thousands of papers, presentations, journal briefs and recorded webinars from the best minds in the Plastics Industry. Spanning almost two decades, this collection of published research and development work in polymer science and plastics technology is a wealth of knowledge and information for anyone involved in plastics.
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Cool Colors in Plastics
Reference to cool colors are those that either absorb a minimum of solar energy or are transparent to solar energy. Last year we presented a paper showing work on colorants that were used in plastics that would meet TSR ratings in coatings applications. We have extended this work into PP, HDPE, PS and TPO.
Structure Development of Polypropylene/Ethylene-Butene Copolymer Blends in Melt Spinning
Polypropylene/ethylene-butene copolymer blends have been melt-spun into filaments. The morphology and orientation of the filaments are studied by SEM, WAXD, and birefringence.
Mechanics of Foam-Filled Honeycombs
Foam-filled honeycombs are prospective core materials for sandwich structures used in cryogenic isolation, hydrogen storage, etc. Mechanical properties of such materials are calculated according the developed models and studied experimentally. Such core has better mechanical properties and resistance to leakage than conventional ones.
The Calorimetric Glass Transition of Free Standing Polystyrene Thin Films
The absolute heat capacity and the glass transition are measured for stacked polystyrene thin films using the step scan differential scanning calorimetric (DSC) method. We find that the absolute heat capacity in both the glass and liquid states decreases with decreasing film thickness and that the Tg also decreases with decreasing film thickness. The results indicate that an understanding of Tg at the nanoscale is elusive.
Measurement of the Bulk Modulus Using Pressurizable Dilatometry
A new piston-cylinder type pressurizable dilatometer controlled by a stepper motor has been developed to measure the time-dependent bulk modulus of viscoelastic materials. The PVT behavior and bulk modulus measurements for polystyrene are reported.
Solid State Structure and Properties of Novel High Performance Olefin Elastomers
Exciting new developments in polyolefin synthesis give rise to blocky olefin copolymers with properties typical of the thermoplastic-elastomers. This paper describes the materials science of these unique polymers including the microphase separated morphology and its relationship to elastomeric behavior.
Unique Material Properties and Potential Applications of Novel High Performance Olefin Elastomers
Polyolefin elastomers are one of the fastest growing product families within elastomers markets. One of the largest usages of polyolefin elastomers is thermoplastic elastomer (TPE) compounds replacing styrenic based TPEs, flexible PVC, TPVs and thermoset rubbers. Recent advancements in polyolefin synthesis have given rise to novel high performance olefin elastomers. Structure-property relationships and markets/applications of these novel high performance olefin elastomers will be discussed in this paper.
Measurement of Fuel Barrier Properties of Rotational Molded Materials
Future California Air Resources Board (CARB) and US Environmental Protection Agency (EPA) fuel emission standards will change the rotational molding industry. This study outlines an apparatus and test method useful to screen various materials relative to these new standards. Quantification of permeation rate and the identification of individual permeating components were conducted on actual coupons from rotational molded parts. A correlation to rotomolded tanks is presented with the preferred material candidates being explained.
NIR Radiation Management Part III - Rational Design of Novel NIR Absorbers for Plastics
At ANTEC 2004 we presented a new class of highly efficient organic NIR absorbers based on the quaterrylenetetra-carboxylic diimide chromophore with a unique performance profile especially suited for laser transmission welding with 808 nm semiconductor lasers and other NIR radiation management applications where high absorptivities at a specific wavelength or in a narrow spectral band (so-called differential" absorptivities) are required.In the first part of this paper we present concepts on how to tune the absorption properties of this class of compounds by intelligent molecular design in order to access other common laser wavelengths. In the second part we will introduce a new class of broad band ("integral") inorganic NIR absorbers with absorption efficiencies hitherto reserved exclusively to organic materials in combination with photo- and thermostabilities typical for an inorganic plastics additive."
Rheological Modeling of Plug-Assist Thermoforming
Solving problems for thermoforming processes in production of axisymmetric thin walled plastics is investigated in this research work. A non-linear viscoelastic rheological model with a new strain energy function is suggested for improvement of physical properties of final product. For model validation, a quantitative relation between stress and technical parameters of plug-assist thermoforming is determined by comparison of theoretical and experimental results. This process with the proposed rheological model could be suggested for prevention from some technical defects such as wall thickness variations, physical instability during inflation-shrinkage, and warpage exhibited in the final part of a polymeric sheet thermoforming.
New Modification Technology for Polymer Composites
Using a unique reactive gas modification technology, new families of polyolefins can be manufactured that have highly oxidized and water-wetable surfaces (figure 1). These functionalized polyolefin particles can be used as performance additives in both thermoplastic and thermoset composites. The unique and highly modified surfaces enable non-polar polyolefins to become compatible with polar polymers. This is seen when the functionalized particles are used in melt blending with engineering plastics, when used as a dispersed solid phase in a thermoset such as polyurethane or epoxy, and when used in a latex paint formulation. When the polyolefin particle integrity is maintained, polymer-polymer composites are formed, which have unique physical properties that often have commercial value.The process of functionalizing the surface of polyolefin particles using reactive gases has many advantages. The process can be done at any scale and in batch or continuous configuration without many of the concerns associated with other unit operations, such as melt phase grafting or liquid processes. Further, the process of using highly reactive gas atmosphere processes, such as those using elemental fluorine initiation, are amenable to modifying most polymers except those that are already highly fluorinated, such as PTFE.
A Review On: 'Stack Mold'
A mold's efficiency is determined by its cores, cavities and levels. Each cavity in a mold forms a single plastic product during each cycle" made by an injection-molding machine.A mold level (or "face") is the flat surface area of the mold containing the cavity. The simplest form of mold is a single-cavity single-level mold where the injection-molding machine injects plastic directly into the single cavity in order to form a molded plastic product. The single cavity can be extended to a multi-cavity layout which increases the number of plastic products molded in each cycle.Multi-cavity molds represent certain engineering challenges which are not present when molding products with a single-cavity mold. In order for the mold to work correctly plastic must be injected into each cavity at exactly the same time. As a result multi-cavity molds require hot runners a system of channels with manifolds designed to deliver molten plastic to each cavity at exactly the same moment. "Although stack molds are not new to injection molding industry they are still surrounded by myths and misconceptions regarding their applications benefits and requirements. The fact is stack molds can meet a variety of molding demands because they are available in configurations that can help users achieve the optimum tooling solution for their application.""
Study of the PTFE Rheology During Paste Extrusion Process
Polytetrafluoroethylene (PTFE) is a remarkable membrane material. Due to its high melting point, PTFE fine powder cannot be processed using conventional molding methods. Instead, techniques involving paste extrusion, rolling and sintering have to be employed. This research builds a simple PTFE capillary rheometer system, with accurate extrusion speed and extrusion pressure control, and investigate the rheology of PTFE paste during extrusion process. Due to the lower constant speed, the density variation of PTFE extrudate decreases from 1.75 g/cm3 (± 5.8%) to 1.68 g/cm3 (± 0.48%). In addition, different lubricant content (18 wt%, 20 wt%, and 22 wt%) was used to monitor the pressure drop at different extrusion speeds (0.5 mm/s, 1 mm/s, 2 mm/s) and reduction ratios (RR=26.47, 47.06, 80.06). It was found that higher lubricant content and high reduction ratio result in lower pressure drop. Lower extrusion speed also results in a better performance in extrudate formation.
Linear Viscoelastic Behaviors of Polypropylene
Polypropylene-layered silicate nanocomposites modified with different levels of maleated polypropylene (PPgMA) compatibilizers were prepared through melt compounding. Above a threshold loading the storage modulus G’ was shown to display a low-frequency plateau. The threshold loading level was found to be strongly correlated with the exfoliation of layered silicates. The samples with higher degree of exfoliation exhibited lower threshold loading level. Such threshold behavior is attributed to the existence, in the quiescent state, of mesoscopic domains composed of correlated silicate layers. Finally, melt rheology also demonstrated that the stress level imposed during melt compounding played an important role in clay exfoliation.
Extrudate Surface Tearing in Extrusion of Wood Plastic Composites
In previous publications from this laboratory it was shown that the phenomenon of wall slip occurs with HDPE filled with rice hulls and HDPE filled with wood flour. In the present work, metallocene polypropylene (mPP) was used as a thermoplastic matrix to investigate the extrudate surface tearing of wood plastic composites (WPC). Maple wood flour, mesh 100, was predried and used as filler at 50 wt.% loading. Maleated syndiotactic metallocene polypropylene and a thermoplastic silicon elastomer (TPSE) were employed as coupling agent and polymer processing aid (PPA) respectively to investigate their influence on the extrudate surface tearing.At loadings of 50 wt.% wood flour in the mPP the extrudates come out of the die with significant tearing and surface roughness. Addition of the coupling agent results in considerable improvement of the extrudates appearance, especially at high output rates. At low throughputs, however, the extrudate surface is still rough. It was found that TPSE at low concentrations (1- 3 wt.%) in the coupled 50% filled mPP composite was able to reduce or even completely eliminate the tearing at all throughputs. Likely, the low viscous PPA forms a lubricating layer on the extrudate surface initiating slip at the wall leading to plug-like flow of the melt flowing through the die. Increasing the screw rotation as well as the concentration of the additive yielded better results.
Isolation of True Runner System Behavior in Simulation Tools for Injection Molding
Obtaining accurate results from simulation tools requires that runners be modeled with mesh details that can identify melt variations in critical, high-gradient regions of the diameter. Modeling runners as beam elements or with inadequate refinement across the diameter may not represent the highly sheared outside laminates as they make their way through the runner system into the molded part. As a result, these simulations fail to identify imbalances in fill which occur in even naturally balanced layouts. In this paper, coarse and refined simulations are compared with runner throughput from an injection mold with a balanced layout to verify the ability to obtain accuracy in simulation, identifying concerns encountered in the process.
Parametric Study to Optimize the Processing Parameters and the Physical Properties of Porous PLGA 85/15 Scaffold
This study investigates the effects of the processing parameters on the scaffold physical properties. Porous scaffolds of PLGA 85/15 were prepared using a gas foaming/salt leaching technique. The processing parameters included: gas saturation pressure, gas saturation time and NaCl/polymer mass ratio. The physical properties considered were the density and porosity of the scaffold. The average pore size and pore density inside the scaffold were also studied. The results showed that for the samples made of NaCl/polymer mass ratio of 1, leaching all the NaCl was impracticable, and the percentage of open pores was relatively low. It was also found that for the samples made of NaCl/polymer mass ratio of 10 and 15, both the saturation time and saturation pressure did not affect the physical properties of the scaffold. However by varying the size or amount of the NaCl particles into the sample, the physical properties of the scaffold can be tailored.
Cure Kinetics of an Epoxy-Amine Adhesive System by Means of Differential Scanning Calorimetry
The cure kinetics of a medical grade epoxy-amine adhesive is studied under dynamic conditions by means of differential scanning calorimetry (DSC), and analyzed using a generalized autocatalytic model of chemical reaction. It is established that the model can be used to determine the degree of conversion, rate of conversion, and the exothermic heat of cure during any curing process with the use of the classical fourth-order Runge-Kutta numerical method. Also, the cure experiments under various quasi-isothermal conditions have been performed and the heat flows of cure measured as functions of cure times, which are then compared with the model calculations. The above numerical approach, coupled with convenient calorimetric cure measurements under dynamic conditions, provides a convenient and reliable tool for developing an oven-curing schedule of the adhesive in medical device industry.
Using TGA to Determine Carbon Fiber Content in Novel Polymer Composites
The objective of this work is to use a TGA (Thermogravimetric Analysis) method to quantify carbon fiber in a novel polymer composite such as PEEK (Polyetheretherketone). Other methods, such as electric muffle furnace, acid digestion, FTIR, and GC-MS are either incapable of detecting carbon fiber content from the composite, time consuming, inaccurate, or very expensive.The role of TGA in plastics industry to identify polymer(s) and filler(s) ratio is not widely used. However its importance has grown. Using TGA to quantify the filler that has similar chemical characteristics as the base polymer is always a challenge. This study applies a modified TGA method to determine the ratio of carbon fiber to polyetheretherketone within +/- 2% accuracy.
Rheological Studies on Radiation Modified Polyethylene Resins
Radiation modification of polyethylene resins prior to end product conversion has brought about significant improvement of various properties of the resins and products made from them using extrusion based processes where the products are formed in the melt phase at different shear rates and extensional rates. Rheological characterizations including Rheotens measurements, capillary viscosity and melt flow stability were carried out on radiation modified HDPE and LLDPE resins and their un-irradiated base resins. It is shown that electron beam irradiation of the resins has significantly enhanced the melt strength due to long chain branching. This effect would be very beneficial to the processability of the radiation-modified resins for applications that demand higher melt strength.
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